The Executive Chalk company is financed only by its own shares, and has $25$ million shares in circulation at a price of $10$ euros each.

a$)$ If the tax rate were $0\%,$ what would be the price of the company and its shares after the buyback process?

b$)$ If the tax rate were $30\%,$ what would be the price of the company and its shares after the buyback process?